Stibnite inverse opal

A 3D photonic crystal (PhC), synthetic opal, has been constructed by self-assembly of sub-micrometre silica spheres and designed for operation in the visible spectral range. Because of its low refractive index contrast (RIC), this PhC does not exhibit a full photonic band gap (PBG), but this property could be achieved by increasing sufficiently the RIC. It is not easy to find a high refractive index material that is transparent in the visible spectral range, but we report here on a method for producing 3D PhC structures with increased RIC, using incorporation of stibnite (Sb₂S₃) into a silica opal PhC. The template is infiltrated with the precursor (Sb[CS(NH₂)₂]₃Cl₃), with subsequent thermal decomposition at 600degC to form Sb₂S₃ in the voids of the opal PhC. Formation of Sb₂S₃ and removal of silica spheres by a chemical etching process can produce a structure that exhibits a full PBG in the visible spectral range. The optical properties of the inverse Sb₂S₃ opal have been measured and compared with theoretical calculations.